Who is Natalia Veselnitskaya, the Russian lawyer who met with Donald Trump Jr.?

The Russian lawyer whom Donald Trump Jr. met to receive information that he thought would be helpful to his father's presidential campaign has campaigned against U.S. sanctions on Russian officials.

The attorney, Natalia Veselnitskaya, met with the younger Trump along with Donald Trump Sr.'s adviser and son-in-law, Jared Kushner, and then–campaign chairman, Paul Manafort, at Trump Tower in New York on June 9, 2016, said Donald Trump Jr.

In a statement received by ABC News, Donald Trump Jr. said an acquaintance proposed a meeting with someone who might provide information helpful to the campaign.

"I was not told her name prior to the meeting," he said of Veselnitskaya, adding that it quickly became clear that she "had no meaningful information."

"Her statements were vague, ambiguous and made no sense," he said. He said she "then changed subjects and began discussing the adoption of Russian children and mentioned the Magnitsky Act."

The Magnitsky Act, passed by Congress in 2012, imposes sanctions on certain Russian officials accused of human rights abuses and was enacted in response to the death of a Russian lawyer and auditor, Sergei Magnitsky. It has become a major issue for the Russian government, which is critical of the law.

Veselnitskaya is based in Moscow at the law firm Camerton Consulting. In the past four years, she has lobbied against the Magnitsky Act, waged a public relations campaign against a key person who backed the law and represented a man accused of involvement in an alleged fraud scheme uncovered by Magnitsky.

When reached by ABC News, Veselnitskaya's office in Moscow did not have any immediate comment.

The Kremlin said today it doesn't know Veselnitskaya.

"No, we do not know who it is, and, of course, we cannot track the meetings of all Russian lawyers, both inside the country and abroad," Kremlin spokesman Dmitry Peskov told reporters Monday when asked if her meeting at Trump Tower was coordinated with Russian authorities.

Background on the Magnitsky case

Magnitsky was a Russian lawyer and auditor who in 2007 and 2008 uncovered an alleged vast corruption scheme involving about $230 million, according to a federal indictment by the U.S. Southern District of New York in 2013. The alleged tax fraud scheme came at the expense of an investment firm, Hermitage Capital, owned by an American investor, Bill Browder, according to the U.S. indictment.

After Magnitsky discovered the alleged fraud, he was arrested and held for almost a year in pretrial detention in Moscow, where he eventually died at age 37, the U.S. indictment alleges. A government spokesperson said at the time that he died of heart failure, but a Russian human rights council found that his detention was unlawful and that he was beaten by guards with rubber batons on the last day of his life and then denied medical care, the indictment says. Russian authorities took a different course and later accused him of having participated in the fraud scheme himself.

Browder launched a campaign to have those allegedly involved in his death blacklisted by the U.S.

In 2012, Congress passed the Magnitsky Act, which freezes the U.S. assets of and places a travel ban on officials allegedly involved in Magnitsky's detention and death. In 2016 the act was expanded globally to cover any officials involved in human rights abuses.

The Kremlin and the Magnitsky fallout

The Kremlin retaliated for the Magnitsky Act, in part, by banning U.S. adoptions of Russian children.

There are indications that some people involved in the alleged fraud that Magnitsky uncovered are being given cover by the Kremlin. Russia issued an Interpol red notice for Browder, which Interpol later rejected as politically motivated. Magnitsky was put on trial posthumously and convicted.

In addition, a number of figures involved in the Magnitsky affair have died in strange circumstances or been poisoned. Most recently, Vladimir Kara-Murza, a well-known Putin critic who played a prominent role in advocating for the Magnitsky Act before Congress, has been hospitalized twice over the last few years after alleged poisonings.

Veselnitskaya's role

Veselnitskaya acted as the lawyer for Denis Katsyv, a key figure in the U.S. indictment. The son of a former Moscow regional transport minister, he was sole owner of Prevezon Holdings, which was named in the U.S. indictment alleging that some proceeds from the tax fraud scheme were laundered through the purchase of New York City real estate.

The U.S. Attorney's Office in New York announced in May that the case was settled, subject to court approval, with Prevezon agreeing to pay nearly $6 million. The settlement specifies that it is a "compromise of disputed claims" and that the defendants denied that the allegations "occurred as described." It adds that the complaint doesn't allege that any of the defendants were "responsible, directly or indirectly, for the arrest, detention or death of Sergei Magnitsky.

Katsyv is not on the list of 44 individuals sanctioned under the Magnitsky Act.

Veselnitskaya has been linked to attempts to cast doubt on the narrative that Magnitsky died under suspicious circumstances.

She has been connected in media reports to efforts to arrange screenings for a film by director Andrei Nekrasov that disputes that Magnitsky uncovered the alleged fraud or that he was beaten in jail.

Radio Free Europe, a U.S.-government-funded broadcaster, reported that an organization Veselnitskaya said she represented paid for a showing of the film at the Newseum in Washington, D.C. An attempt to screen the film at the European Union Parliament was abruptly canceled. Other European channels have dropped the film, after Browder threatened to sue for defamation.

Human rights activists involved in the investigation of Magnitsky's death dismissed the film as an attempt to whitewash torture.

Contacted by ABC News on Monday, Nekrasov disputed the notion that Veselnitskaya has been involved in arranging any screenings or broadcast agreements for the film.

She has appeared on Russian television, condemning the Magnitsky Act and arguing that Magnitsky was not murdered and that Browder, for his own purposes, invented the notion that Magnitsky was killed.

During a television discussion in December 2014, Veselnitskaya put forward a Kremlin talking point that the Magnitsky Act was passed as a political weapon by the U.S. with his death a pretext.

"It is an absolutely fake statutory act in the United States of America that has nothing to do with Sergei Magnitsky but which was adopted for absolutely other political purposes," she said on RBC, an independent Russian channel.

"There is no such case," she said of Magnitsky's death. "There is only the case of Browder, who has used the death of this poor young man for his absolutely own personal interests."